The University of Chicago Cancer Research Center DNA Sequencing Facility provides automated DNA sequencing services. The goals of the Facility are to provide accurate sequences at the lowest cost and the fastest turn- around time possible. The Facility includes an ABl 377 automated sequenator, 92-well and 48-well thermal cyclers, a Macintosh computer, a high resolution printer, and several software packages for sequence editing and alignment, including the latest version of Sequencer form Gene Codes. Users obtain order forms from the Facility World Wide Web page, fill them out (including the names and descriptions of each DNA template to be sequenced), place them in a personal file at the Facility, and then deliver a hard copy of the order together with the DNA samples. Facility technicians run the cycle sequencing reactions, usually dye- terminator reactions with primers supplied by the users, and then the sequencing gels, each with 36 lanes. The resulting chromatograms are placed in each user file, from which they can be down-loaded for editing and alignment. Turn-around time is 3-4 days. Routine results give good sequence for 600 bases; some templates can be read beyond 800. Facility staff provide users with advice on cloning vectors, template preparation, and planning of sequencing projects.